Radial flow disk filter

ABSTRACT

A radial flow filter having fixed end caps, a stack of annular filter discs having their outer edges secured in fixed positions disposed between the end caps, said discs preferably having surface grooves, a pervious center tube, and a discharge outlet in one of said end caps.

United States Patent I/AIII/ 57 40/42,

{72] Inventor Southwick W. Briggs 2,553,820 /1951 Gunn 210/492 ChevyChme, Md. 2,583,423 1/1952 Hallinan 210/488X [21] App]. No. 824,3282,692,685 /1954 Garland 210/488 [22] Filed Feb. 3, 1969 2,702,637 2/1955Shepard 210/492 Patented Feb. 16, 1971 2,751,085 6/1956 Bowers et al.210/488 [73] Assignee William A. Brazerol 3,214,368 10/1965 Muller2l0/488X hi g mq FOREIGNPATIENTS mama 537,144 2/1957 Canada 210/488569,626 l/l959 Canada 210/494 Great Britain 2 1 5 Claims, 6 DrawingFigs. Primary Examiner-Reuben Friedman 52] 210/457, AssistanrExaminerC.M. Ditlow 2 0 4 4 2 0, 2 Attorney-Stepno and Neilan [51] hit. (I 80125/18 Field of Search 210/457, 484, 488, 489, 490, 492, 497, 498; /278,488,

489 ABSTRACT: A radial flow filter having fixed end caps, a stack 56 R rCited of annular filter discs having their outer edges secured in fixed1 e fences positions disposed between the end caps, said diskspreferably UNITED STATES PATENTS having surface grooves, a perviouscenter tube, and a 2,354,380 7/1944 Ka s t en.. 210/488 discharge outletin one of said end caps.

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Patented "Feb. 16, 1971 v 3,563,388

2 Sheets-Sheet l ATTORNEY RADIAL FLOW DISK FILTER The presentapplication relates to a radial flow filter assembly comprising a stackof annular discs of a suitable filter medium with the outer edges of thediscs being secured in fixed positions. The flow of oil or other fluidto be filtered is radially inwardly between the discs into an axialpassage leading to a discharge outlet in one or both of the end caps.

It is an essential feature of the invention that the outer periphery ofeach of the annular discs is adhesively or otherwise fixed in position,for example, by being secured to an annular fluid permeable supportmember.

Although disc pack filters are known in the prior art, heretofore, theouter edges of the discs have not been secured, and the stack of discswas free to expand and contract. Usually, a takeup harness or otherspring arrangement is employed in known disc pack filters to adjust theheight of the disc pack. When oil flows through the disc pack, the fluidpressure expands the disc pack against the action of the harness, andwhen the fluid pressure ceases, the harness com 1 presses the disc pack.However, with such prior art arrangements, it has been found that thefluid pressure frequently opens channels through the disc pack throughwhich the oil flows without being filtered. Furthermore the prior arttakeup harness or other spring means associated with one of the endplates of the disc pack, when the fluid pressure is removed, maycompress the disc pack too much so that the flow paths between adjacentdiscs are closed, or the harness may fail to compress the disc pack toits original size. In the latter case, channels will eventually fonnthrough which liquid will flow without being filtered.

In contradistinction, the present invention employs annular discs whichare secured at their outer peripheries to relatively rigid means so thatthe outer peripheries of the discs are fixed relative to each other.

It is a further feature of the invention that no take up harness orsimilar spring means isrequired to compensate for changes in the heightof the stacked annular discs.

According to one aspect of the invention, the annular filter discs maybe constructed to selectively remove particles of a particular sizedistribution, for example, relatively fine particles from the fluidbeing filtered.

Tests have shown that the filter assembly of the invention is superiorin operating characteristics to a conventional prior art all pleatedpaper filter of the same outside dimensions as the filter of theinvention.

On the basis of test data obtained during laboratory accelerated sludgeaddition tests, it has been concluded that, compared to a pleated paperfilter, the filter assembly of the invention has substantially increasedlife and is more effective in removing particles from the fluid beingfiltered. Although the initial cost of the filter of the invention maybe higher, this higher initial cost is more than compensated for by theincreased life which leads to reduced maintenance costs, increasedefficiency of filtration, and increased operating time before servicingis required.

It is a principal object of the present invention to provide a filterassembly having increased efficiency and/or longer life.

Another object of this invention is to provide a stacked annular discfilter in which the outer edges of the discs are held in fixed positionsduring operation.

Still another object of this invention is to provide a stacked annulardisc filter in which a fluid pervious wrap or casing is adhesivelybonded to the outer peripheries of the discs.

A further object of the invention is to provide a stacked annular discfilter which does not require a takeup harness or similar means tocompensate for changes in height of the stack of annular discs.

The above and other objects, features and advantages of the inventionwill become more apparent as this description proceeds and from theaccompanying drawings wherein:

FIG. 1 is a plan view of one embodiment of an annular filter discelement contemplated by the present invention.

FIG. 2 is an elevational view, partly in section, of a filter assemblyemploying filter discs of the type shown in FIG. 1.

FIG. 3 is a plan view of another embodiment of a filter disc inaccordance with the invention, which disc has a hexagonal periphery.

FIG. 4 is an elevational view of a filter assembly employing filterdiscs of the type shown in FIG. 3.

FIG. 5 is a sectional view on an enlarged scale of a plurality of filterdiscs of the invention shown in stacked relationship.

FIG. 6 is a graph comparing the operating effectiveness of a filterassembly of the invention with a pleated paper filter of correspondingsize.

Referring now to the drawings, and more particularly to FIG. I,reference numeral 10 designates an annular filter disc which hascircular inner and outer peripheries l2 and 14, respectively. In thisembodiment, both surfaces of the disc 10 are preferably cross embossedto provide therebetween a network of intersecting channels or grooves 16so that when a plurality of the discs are arranged in stackrelationship, excellent drainage will be afforded to fluid passingradially between adjacent discs.

The discs 10 may be made of any suitable fibrous material known in theart for use in such filters. Preferably, the discs are made of cottonpaper of about 30 point which is lofted to about 35 point in theembossing process to form the grooves 16. On the other hand, if thediscs are made of a so-called open material such as pound basis weight60 or 70 point linter paper, such a material has sufficient surfaceirregularities to entrap particles without embossing. While not wishingto be bound by any particular theory, it is theorized that the stackeddiscs I0 function to remove fine carbon particles and the like from thefluid being filtered by entrapping the particles throughout the fulldepth of the: discs.

With reference to FIG. 2, a plurality of stacked discs I0 are surroundedby a fluid permeable outer wrap or casing I8 which is secured to theouter peripheries of the discs 10, preferably by an adhesive. Arelatively rigid perforated center tube 20 constituting an axialpassageto collect filtered fluid may be disposed within the innerperipheries 12 of the discs and extends between upper and lower end caps22 and 24. The end caps are maintained in fixed relationship withrespect to each other by the relatively rigid center tube 20 and/or byouter fluid permeable support member which may be a perforatedcylindrical metal casing 10. As shown in FIG. 2, there is a dischargeport 26 in the lower end cap 24 through which the filtered fluid leavesthe filter assembly for further use.

The annular discs 10 may be secured to the perforated casing 18 in anysuitable manner. By way of example, the annular discs may be stackedupon a mandrel and compressed slightly e.g. about inch for a 35 point,30 inch length filter. This assembly may then be inserted into theperforated casing I8 which may have an adhesive on its inner surface.The mandrel is thereafter removed, and if a center tube is to beemployed, the perforated center tube I2, which is not adhesively securedto the discs, is inserted. Any suitable adhesive which will withstandthe operating conditions may be employed. One suitable adhesive is apolyvinyl acetate-phenolic resin adhesive.

The casing 18 to which the outer peripheries 14 of the annular discs 10are bondedis of sufficient rigidity to withstand the operating pressureswhile maintaining the preset spacing of the discs. If casing 18 issufficiently rigid to space the end caps, no center tube is necessary. Arelatively rigid wire mesh or screen may optionally be used in lieu ofcasing 18. Where a rigid center tube is employed, the outer supportmember may be a flexible mesh, the outer support member may be aplurality of taut strings or straps or any comparable means which may beadhesively bonded to the outer edges of the discs 10 to hold them infixed position.

If desired, the filter discs 10 may be partially or completelyimpregnated with a phenol formaldehyde resin or other suitablethermosetting resin in order to provide increased rigidity andresistance to the materials to be filtered.

In order to further improve the filtering ability of the annular discs10 and fluid distribution through the spacings between the discs, it iswithin the purview of the present invention to rotate each disc relativeto the adjacent disc.

FIGS. 3 and 4 illustrate another embodiment of the invention in whichannular discs 28 have a hexagonal outer periphery, a circular innerperiphery 12, and intersecting grooves or channels 16 provided by crossembossing or similar means as described in connection with the FIG. 1embodiment. The hexagonal outer configuration of the discs 28 ena blesthe discs to be cut from large sheets or webs with the production ofless scrap.

In FIG. 4, the discs 28 are incorporated within and fixedly secured tothe inner surface of a fluid permeable outer wrap or casing 30 which hasthe form of a hexagon in plan to conform with the configuration of thediscs 28.

It will of course be appreciated that a perforated center tube such asthat of FIG. 2 may extend between the end caps 32 and 34 of the FIG. 4embodiment, and that a discharge port is 7 provided in one or both ofthe end caps 32 and 34. in this embodiment, the end caps are held infixed position relative to each other by the perforated hexagonal casing30 and/or by the center tube. In this embodiment, like in the embodimentdescribed previously, no takeup harness or similar means is necessary.

FIG. 5 illustrates three stacked annular discs of the invention invertical cross section to show in greater detail the grooves 16 whichmay be provided in both surfaces of the discs.

FIG. 6 is a graph comparing the operating characteristics of a filter inaccordance with the FIG. 1 embodiment of this application with a pleatedpaper filter of corresponding size. The data used in preparing the graphwas obtained from conducting accelerated sludge addition tests upon thefilter of the invention and upon the pleated paper filter. The samequantity of oil and the same operating temperature were employed in bothcases. The flow rate was 60 gallons of oil per minute, and 1 pound ofsludge was initially present and an additional pound was added every 45minutes. As a rule of thumb, 6 hours of the accelerated sludge additiontest are equivalent to l-2 months use in the field as an oil filter in alocomotive.

ln HO. 6, the percent light transmission through the oil and thedifferential pressure in pounds per square inch are plotted on theordinate, and time in hours, and the amount of sludge added in poundsare plotted on the abscissa.

Curve A is a plot of the light transmission employing the pleated paperfilter while curve B is a plot of the light transmission employing thefilter of the invention. As is apparent from these curves, there issubstantially more light transmission through the oil for the first4%hours of the test employing the filter of the invention. This meansthat the filter of the invention has removed more particles from the oilas evidenced by the higher light transmission. After about 4.5 hours,the light transmission employing the pleated paper filter has reachedits lowest point and thereafter increases somewhat whereas it isapproximately 8% hours before cure curve B reaches its lowest point. Theincrease in light transmission after 4.5 hours for curve A and afterabout 8% hours for curve B is believed due to the accumulated sludge onthe filters being effective to filter out additional sludge.

Curves C and D are plots of the pressure differential across the filterwith time employing the prior art filter and the filter of the presentinvention, respectively. As is clearly shown in FIG. 6, curve C risessharply after about 4 hours which is an indication of a rapidlyincreasing pressure drop across the filter caused by clogging of thefilter. It is clear that after about 6 hours, curve C has risen to apoint where, if this was an actual operating installation, e.g. on adiesel locomotive engine design pressure drop may be about to beexceeded causing opening of a safety valve and reduced filtering of theoil, or shutdown of the engine. On the other hand, the pressure dropacross the filter of the invention as indicated by the plot D remainssubstantially constant at about 8.5 p.s.i. even after 9 hours when thetest was stopped. From this data it is apparent that the filter of theinvention is not only more efficient in cleaning the 011 but also has asubstantially longer life as compared to the pleated paper filter.

While preferred embodiments of the invention have been shown anddescribed with particularity, it will be appreciated that minor changesand modifications may suggest themselves to those of ordinary skill inthe art upon being apprised of the present disclosure. It is intended toencompass all such changes and modifications as fall within the scopeand spirit of the appended claims.

lclaim: I

l. A filter comprising a plurality of fluid pervious filter elements,each of said elements being comprised of a filter paper and having apair of oppositely disposed side surfaces, said oppositely disposedsurfaces being impressed with a-grid pattern comprising a plurality ofintersecting grooves, said elements having inner and outer peripheries,said elements being in compression and stacked one upon another with theland areas between said grooves in contact surface-to-surface; a fluidpervious outer wrap adhesively bonded to the outer peripheries of saidelements to maintain the outer peripheries of the elements in fixedrelationship with respect to each other and to maintain the elements incompression and control the depths of the grooves; a fluid pervious tubeextending through said stacked elements and being in contact with theinner peripheries thereof; and an end cap on each end of said stack ofelements, said end caps contacting said tube and outer wrap andrespectively contacting the outwardly disposed surface of the filterelement defining the adjacent ends of said stack, at least one of saidend caps having. a discharge port therein which communicates with theinterior of said tube.

2. A filter comprising a plurality of fluid pervious filter elements,each of said elements being comprised of an annular disc of a filterpaper and having a pair of oppositely disposed side surfaces, saidelements being in compression and stacked one upon another, a fluidpervious cylindrical outer member bonded to the outer peripheries ofsaid elements to maintain the outer peripheries of the elements in fixedrelationship with respect to each other and to maintain the elements incompression, an axial passage through said elements for collectingfiltered fluid, and an end cap on each end of said stack of elements,said end caps contacting said cylindrical outer member and respectivelycontacting the outwardly disposed surface of the filter element definingthe adjacent ends of said stack, at least one of said end caps having adischarge port therein which communicates with said passage.

3. A filter according to claim 2, further comprising means to adhesivelysecure the outer periphery of each of said annular discs to saidcylindrical outer member.

4. A filter according to claim 2, wherein said annular discs haveunsecured inner peripheries.

5. A filter according to claim 2, wherein said annular discs are made of60-70 point linter paper.

1. A filter comprising a plurality of fluid pervious filter elements,each of said elements being comprised of a filter paper and having apair of oppositely disposed side surfaces, said oppositely disposedsurfaces being impressed with a grid pattern comprising a plurality ofintersecting grooves, said elements having inner and outer peripheries,said elements being in compression and stacked one upon another with theland areas between said grooves in contact surface-to-surface; a fluidpervious outer wrap adhesively bonded to the outer peripheries of saidelements to maintain the outer peripheries of the elements in fixedrelationship with respect to each other and to maintain the elements incompression and control the depths of the grooves; a fluid pervious tubeextending through said stacked elements and being in contact with theinner peripheries thereof; and an end cap on each end of said stack ofelements, said end caps contacting said tube and outer wrap andrespectively contacting the outwardly disposed surface of the filterelement defining the adjacent ends of said stack, at least one of saidend caps having a discharge port therein which communicates with theinterior of said tube.
 2. A filter comprising a plurality of fluidpervious filter elements, each of said elements being comprised of anannular disc of a filter paper and having a pair of oppositely disposedside surfaces, said elements being in compression and stacked one uponanother, a fluid pervioUs cylindrical outer member bonded to the outerperipheries of said elements to maintain the outer peripheries of theelements in fixed relationship with respect to each other and tomaintain the elements in compression, an axial passage through saidelements for collecting filtered fluid, and an end cap on each end ofsaid stack of elements, said end caps contacting said cylindrical outermember and respectively contacting the outwardly disposed surface of thefilter element defining the adjacent ends of said stack, at least one ofsaid end caps having a discharge port therein which communicates withsaid passage.
 3. A filter according to claim 2, further comprising meansto adhesively secure the outer periphery of each of said annular discsto said cylindrical outer member.
 4. A filter according to claim 2,wherein said annular discs have unsecured inner peripheries.
 5. A filteraccording to claim 2, wherein said annular discs are made of 60-70 pointlinter paper.